Spring and method of making the same



A. IJ. BRG Erm. SPRING AND vuxrs'rcHolioFjMAKING `Tms: SAME May"13,l1941.

original Filed'nec. vs, 193'? k/ l l 22j lar/4 lNvx-:N'roRs ALFRED J.BERG l0/'IN 0. HUSE ATTOW als Patented May 13, 1941 SPRING AND VMETHOD FMAKING THE SAME Alfred J. Berg, Portsmouth, lN. H., and John 0.

Huse, United States Navy Original application December 8, 1937, SerialNo.

Divided andthis application Decem ber 15, 1939, Serial No. 309,419

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 5 Claims.

Our invention relates primarily to a new and useful spring and method ofmaking the same.

In the pri-or art, springs have been made from round or angular shapedwire or flat, straight strips of metal, which have been helically coiledabout a mandrel which has been revolvably mounted in a lathe or similarmachine tool to rotate about the longitudinal aXis of the mandrel withthe initial end of the wire or strip secured in the machine. The wire orstrip is held, for instance, in the tool post of the lathe where thewire or strip is subjected to considerable longi-V tudinal stress as itis wound about the mandrel by the operation of the lathe or tool. Thepitch of the spring is afforded by the rate of longitudinal motion ofthe tool post relative to the rate at which the lathe or tool rotatesthe wire or strip about the mandrel. The holding of the strip by thetool post is usually in the form of a clamp having an opening throughwhich the wire or strip extends onto the mandrel, and which openinggrips with substantial pressure the surface of the wire or strip as itis drawn through the clamp opening. The amount of pressure exerted bythe clamp opening upon the surface of the wire or strip controls the setof the spring, which, with the external diameter of the mandrel aboutwhich the 'spring is coiled controls the internal diameter of thespring.

This practice of making springs, which has been followed from theearliest times, is tedious and expensive, requiring the manufacture ofthe metal into wire or strips, which is a relatively expensive form ofmetal, and then the turning or the springs in a lathe or similar tool,as above explained, which adds materially to the cost of the metalcontained in the springs.

According to our invention, metal in the relatively cheap form of whatis known as bar stock is mounted in a lathe, screw machine or similartool, and rotated about its longitudinal axis, and the spring of thedesired di-mensions is sheared progressively from the end ci Vsuch barstock while the same is being rotated in such machine. The bar stock maybe formed of cast, drawn or extruded metal. When such 'bar stock isformed on the one hand of cast metal or on the other hand of drawn orextruded metal, the characteristics of the spring helically turnedfromthe end thereof is correspondingly different. Such difference residesnot only in the inherent characteristics of the cast metal on the onehand and the worked metal on the other, and such separatecharacteristics are each improved .for spring purposes Vby the characterof the tool employed to helically cut the spring from the end of the barstock, due to the working of the metal by such tool. We have found thata thin tool, that is, a tool in which the metal below its cutting edgeis relatively thin, will cold work the metal of the spring to someextent While the same is being severed 4by such tool from the end of thebar stock. Whilesuch cold working may aord .some slight change in thecharacteristics of the metal of the spring as severed from the end ofthe bar stock, we have found that such characteristics vare of littlebenet for spring purposes, and that substantial cold working of suchmetal While being cut transforms its char-V acteristics into those veryadvantageous for spring purposes. Pursuant to such nding, We have.discovered that :such substantial cold working maybe accomplished While.and by cutting metal with a cutter of ,abnormal Vtop and side rakes,either or lboth .of which `sulcvstantially.inf crease the force requiredto cleave the metal spring from a ylarger ,piece `of metal, and thatsuch increased force `may be `afforded by em? ploying a cutting tool .ofnormal top and side rakes but having .one or more relatively shallownicks vin its cutting .edge with a corresponding groove extending fromsuch inick, or nicks, across at least a part 0f the side rake Ior:beveled surface of the cutter, that 'the cold `working characteristicsof the spring vhelically cut by such cutter from the end of bar stockwill greatly improve the metal of such spring and increase Vits .usefullife `and electiveness for spring Purposes. Each of these nicks `and`associated,grooves respectively in the cutting edge or top vrake andacross jthe beveled surface or `,side rake of the cutter cause acorrugation to be formed in the thus severed spring. Any number of thesecorrugations may be employed in the Width ofthe spring, and eachcorrugation `adds to the strength, resiliency and freedom from Abreakageor fracture of the spring, and enables a spring of a given strength tobe produced from much thinner metal of lesser weight and cost than hasheretofore been possible.

Likewise, a spring .of greaterstrength may be produced from .thethickness of `metal heretofore employed for making springs according toprior practice.

We have also found that Whena cutting or turning tool with abnormal'topand side rakes, and any or all of theother means herein disclosed, is

employed, very satisfactory springs .of greater' cold workedcharacteristics .are :cut or turned therebyfrom Va cheaper form of metalthan has art to also apply to the production of flat springs byproviding the cutter normally adapted for such cutting with the cuttingedge and its beveled surface with the features of our invention.

We have also found that by severing the spring helically from the end ofthe bar stock by a cutter having metal of subst-antial width supportingits cutting edge, so that the spring as thus severed from the end of thepart is extended initially.

at al Wide angle from the surface of the end of the bar, such severedspring is thereby substantially improved in its spring characteristics.This improvement is due to the resulting cold working of the metaloccurring simultaneously with its severance from the end of the bar. Inth-e severance of such spring, it may be observed that the end of thebar, from which a preceding portion of the helical spring has been cut,has a bright Yand glossy appearing surface, while the outer surface .ofIthe helix as the same is being severed from the bar and passed over theside rake or beveled surface of the thick portion of the cuttersupporting the bar, the outer surface of such severed portion ofthehelix commencing opposite the point of severance from the bar, istransformed from such bright surface to a dull one,V or the appearanceof sand blasted glass, or has a frosted appearance. This transformationis due to the peculiar cold working of the metal as itis beingsevered.Such transformation appears to be Vdue to a compression of the metal asit is severed to form the spring, and which compression seems to belocalized upon that side ofthe severed spring which is not contacted bythe cutter in its severance from the part, while the V'opposite surfaceof the severed spring in contact with the cutter in such severance, isalso cold worked.: This latter cold working seems to be a stretching ofthe severed metal together with its polishing contact with the beveledsurface of and supporting the cutting edge of the cutter.

This different cold working of opposite surfaces of the severed springwe have found very advantageous and beneficial in springs as affordinggreater resiliency, strength, and freedom from breakage or fracture ofthe spring, which enables'a spring of a given strength to be producedfrom much thinner metal of lesser weight and cost than has heretoforebeen possible. We have also found that when this last named cold workingis aiforded by a tool whose cutting edge is provided with the aforesaidnick or nicks, each having a corresponding groove extending over atleast a portion of its beveled surface, that such beneficialcharacteristics are greatly improved, so that a much superior springresults or that an equal spring is made of far lighter metal and lesscost.

Other features and advantages of the invention will appear in thespecification.

In the drawing, in which like reference characters indicate the samepart,

Fig. 1 is a side elevation view of a spring embodying our invention;

Fig. 2 is a top plan view thereof; Fig. 3 is a cross-sectional Viewtaken through 'one portion of such spring;

Figs. 7 and 8 are respectively end and side elevation views of a toolfor turning the spring from the end of a bar;

Figs. 9 and 10 are respectively views similar to Figs. 7 and 8, but of adifferent such tool;

Fig. 11 is a side elevation View of the forward portion of a differentlyconstructed tool, similar to Figs. 8 and 9.

Fig. 12 is a side elevation View, partly in central vertical section, ofa bar from the end of which the spring may be turned by the tools Shownin Figs. '7 and 8;

Fig. 13 is a side elevation view cf a bar from the end of which aportion of the spring has been turned by the tool shown in Figs. 8 and 9or the tool shown in Fig. 11;

Fig. 14is a side elevation view of the end portion of a bar with theinitial portion of the spring turned from the end thereof by a cuttingtool whose cutting end is shown in cross-section; and

Fig. 15 is a' top plan view of, for instance, the tool of Figs. '7 and8, beside which is a turning tool for truing up the exterior diameter ofthe bar stock in advance of the helical turning of the spring from theend thereof, and both of which tools lare to be clamped in the tool postof the lathe or othermachine-tool in which the bar stock is revolvablymounted.

A metal bar I0, Fig. 12, which may be cylindrical or of any desiredexterior shape corresponding to the exterior shape of the desiredspring, may be mounted in the chuck of a lathe, screw machine, or otherturning machine-tool. Said bar has a longitudinal opening II extendingcentrally therethrough. The shank I2 of a turning tool, Figs. 7 and 8,is placed in the tool post of the before-mentioned machine-tool. Theforward upper edge I3 of shank I2, which comprises its sharp cuttingedge is formed at the top of the relatively broad forward portion I4 ofsuch tool. The lateral clearance surface I5 of portion I4 extendsdownwardly from said edge I3 at a slight angle to avoid friction-alcontact with the end of the bar from which a portion of the spring hasbeen severed, while the opposite lateral surface I6 of said portion I4extends downwardly from said edge I3 at a wide angle, extendingpreferably to the lower edge of said portion I4.

In operation, the bar I0 is rotated by the machine-tool. 'Ihe shank I2of the turning tool is rigidly mounted in the tool post of suchmachine-tool With-the point of said cutting edge I3 extending within theopening or bore I I in bar I0. The above stated machine-tool and itstool post are not illustrated, as the same are well known, and any ofthe various forms of such machinetools may be advantageously employed inwhich the tool post is adapted to move longitudinally toward and intothe end of the bar I0 at a rate proportionate to the speed at which thebar I0 is rotated. The rate of such longitudinal movement of the toolpost determines the thickness of the spring to be cut from the end ofthe bar, while the width of the spring so cut is determined by thethickness of the wall of the tubular bar I0. As the` cutting edge I3 ofturning tool shank I2 commences and continues to cut into the end of themetal bar IIJ, pursuant to the rotary motion imparted to bar I0 by saidmachinetool and to the longitudinal relative motion of the tool post inwhich is mounted the turning tool shank I2, the helical spring II ishelically cut from the end of bar II'I by said cutting edge I3. In suchcutting, the surface I5 of portion I4 of turning tool shank I2 is, byits aforesaid slight angularity, out of frictional contact with the endof the metal bar from which the spring I7 is being turned. In thehelical turning or cutting of the helical spring -II from the end of themetal bar, the portion of the spring being severed from the bar isforced downwardly and outwardly in rm frictional contact with saidYsurface I6 of portion I4 of turning tool shank I2, and in substantialifrictional contact therewith. This turning is done at room temperature,but the force and friction required in such cutting of the spring I'Ifrom the end of the bar results in substantial heat being impartedmainly to the portion of spring I'I being severed from the end of themetal bar. In such severance it is believed that the surface portion ofthe spring I1 being severed by the cutting edge I3 and passed downwardlyover the angular surface IIS of portion I4 of the turning tool shank I2,is subjected to a stretching action, as well as to substantialfrictional action in its passage over said surface I5. For instance,when the spring I'I is cut from the end of a copper bar, the surface I3ofthe end of such bar from which a portion of the spring has been cut isvery bright, as well as smooth, as is the surface of the cut springwhich passes over the surface IS of the portion It of tool shank I2.Substantially at the point I9, in Fig. 14, where the severed portion ofthe spring I'I commences to deflect from` the surface I8 of the end ofthe bar from which the spring is being turned, the outer surface of thespring I'I is transformed into a dull iinish or appearance, whichsimulates a frosted appearance, or that of a :sand-blasted surface.Since every part of spring il must pass said point I9, the whole of saidsurface of the thus severed spring has a uniform dull or frosted finishor appearance. This dull or frosted appearance is believed to be due tothe metal comprising said surface of the spring Il being subjected bysuch progressive severance to substantial compression, which issuccessively and uniformly imparted to the spring as it is severed fromthe bar of metal. lThis severance of the spring from the barsimultaneously affords to the opposite surfaces of the spring I'I a coldworking which is different in kind upon each of said surfaces, since thephysical appearance of said severed surfaces is substantially different.We have found that saidcold Working of opposite surfaces of the springIl is very beneficial and that it increases the strength, efficiency,durability, and freedom from breakage of the spring of a given weight ofmetal, or produces a spring of equal strength, efficiency, durability,and freedom from breakage of the spring whenvmade from thinner and,consequently, lighter metal, with resulting decrease in cost per spring,due to the saving of weight, apart from the further substantial savingin the production cost of the spring aiorded by our invention. Y

The opening or bore II extending longitudinally through the bar It maynormally control the size of the opening 2t through .the center of thespring I1, shown in Figs. 1 and 2. However, by manipulation of thecutting edge I3 of the turning tool shank I2, the size of said opening253 in spring II may be larger or smaller than the opening or bore II inbar i0. Such manipulation comprises a setting in the tool post of theshank I2 of the turning tool such that its cutting edge I3 extendstoward its point or outer end at a l slightly downward angle. The sizeof the opening 2i] through spring I'i may thus be made less inl diameterthan the 4opening or bore II in vbar I0; while, when the cutting IedgeI3 is adjusted in the -tool post to extend at a slightly upward angletoward its point or outer end, the diameter of the opening 2U throughspring I is made somewhat smaller than that of the opening or bore I inbar I0. This variation in the diameter of the opening 20 is .due tothestated angularity of the cutting edge I3 exerting an inward oroutward thrust progressively `upon the spring I -'I as it is beingsevered from the end of the bar of metal.

The :before-stated cold working characteristics of the spring areimparted simultaneously with its cutting from the end of a bar ofcopper, 4and similar cold Working characteristics likewise appear whenthe metal ba-r is of met-al other than copper. I

The dimensions of the spring in the width and thickness -of each helix`are matters which may vary as to the thickness of each helix, accordingto the rate of longitudinal movement of the tool post tothe turningspeed of the metal bar; while the Width of each helix is determined bythe thickness of the bar I0 from its opening or bore I I to itscircumference The spring heretofore described is of any shape which thebefore-stated conditions may produce.

The corrugation, or corrugations, in the spring substantially shown inFigs. 1 6, inclusive, and the manner-of making the same will now bedescribed.

In the sharp cutting edge I3 of portion I4 of tool shank I2, Figs. '7through 11, .is formed one or more nicks 2| from which extends across atleast a portion of the surface I6 of portion I 4 a depressed groove 22.'In Figs. l through 10 said groove 22 extends completely across saidsurface I 6, while in Fig. l1 said grooves 22 extend only partiallyacross said surface I6, by reason of the fac-t that the bottoms of thegrooves 22 are at a Wider angle than said surface I6, which results insaid grooves 22 fading out as it were after they traverse only a portionof the width of the surface I6 from said edge I3. The helices of thespring I1 may have any number of corrugations 23 therein extendinghelically along the juxtaposed surfaces of the helical spring, and whichcorrugations 2t are Aformed each by a corresponding nick 2| and grooves22, respectively, in the edge I3 and surface I 5 lof portion I4 of theturning tool shank I2, and which corrugations 23 are formed in saidspring I1 simultaneously with the spring being turned or cut from theend of the metal bar. The formation of said corrugations 23, eachcomprising a convex Yridge 24, which substantially conforms to the shapeof nick 2I and groove 22 aforesaid, extending from and helically alongone surface of each helices of spring I'I, and upon theopposite surfaceof each helices of spring Il is la concave valley 25 registering withsaid ridge 24, Any number of corrugations 23 may be formed in the springaccording to the number of nicks 2l and grooves 22Y in the turning tool.Each of said corrugations 23 in said spring materially increases thestrength, e'iciency, durability V4and freedom from breakage of thespring, or produces a spring of equal strength, eiiiciency, durabilityand freedom from breakage when made 'from thinner and, consequently,lighter material, with resulting decrease in cost per spring, due to thesaving of weight, apart from the fur-ther substantial saving in theproduction cost of the spring afforded by our invention.

,For instance, ina spring of relatively `short length having onecorrugation therein, substantially as shown in Figs, 1, 2 and 3, thesame Was fully compressed some 10,000 times without apparentdiminishment of the length and strength of the spring.

In the helical turning of the spring from the end of the bar Ill therotary motion of the severed portion of the spring, with the bar III, bythe lathe or other turning tool, causes the severed portion of thespring I1 to be Whipped about. This is liable to break the spring or todo injury to persons or property. To avoid this liability a rod 2B isextended longitudinally of the bar I into its opening or bore II.This'rod 26 is adapted to be carried or supported by the aforesaid toolpost or any other portionof the machine-tool, and is adapted to receiveand support the severed portion of the spring, by such severed portionof the spring surrounding such rod 26 and by maintaining the same inalignment with the bar IIl from which the spring is being severed.

In Fig. 13 is illustrated a solid bar of metal Ia having no opening orbore therethrough, with a portion of the spring I1 helically turnedtherefrom and supported by la central integral round bar of metal Ibprojecting longitudinally from the center of the end of bar a, fromwhich the portion of spring I1 has been severed, said bar Illbsupporting the severed portion of the spring I1 by loosely engaging inthe central opening of spring I1. Said bar Ib is simultaneously formedby the helical cutting or turning of the spring I1 from an end of thesolid bar Illa with a single tool, as shown in Figs. 9 yand 10, or thatshown in Fig. 11, and Without the formation of :a shaving or cuttingother than the severed portion of the spring I1 or the said bar Illb, sothat no Waste of metal may occur in the helical turning of `a spring ofour invention from the end of ia solid bar of metal Ia.

In the turning of the helical spring from the end of tubular bar I0,Fig. l2, the outer end or point of the cutting edge I3 performs nocutting at its point, because such point extends into the opening orbore II in the center of the said bar I0. However, in turning the springI1 from the solid bar Ia, Fig. 13, with a single cutter and Without ashaving other than the spring I1, the outer or point end of the cuttingtool is substantially constructed, in accordance with our invention, byproviding, Fig. 11, commencing at the outer end of the cutting edge I3,la. cutting edge I3a, which at its top merges into the cutting edge I3,and extends downwardly therefrom along the outer or forward margin ofthe surface I6 of portion I4. The outer terminus of portion I4 of theturning tool shank I2 comprises a surface Ma, one of whose margins isthe cutting edge I3a, another of which margins is the outer edge of thelateral surface I5 of portion I4, which said surfaces I5 iand I6 apex atthe cutting edge I3, while the remaining edge of said surface Ida is thebottom of portion I4 of the turning tool, said surface IIIa extending ata slight angle from the cutting edge I3a downwardly toward the shank I2of the turning tool, the lowest point of such inclination being at thelower edge of portion I4 at the point therein which is joined by thelower terminus of said surface I5. In helically turning the shaving fromthe end of the solid bar Illa with the tool of Fig. 11, the procedureheretofore described relative to Figs. '7, 8, and 12, may be followed,except that the point ofthe turning tool of Fig.

11, comprising the juncture of the cutting edges I3, I3a, is set at theouter diameter of the bar IIlb, Fig. 13. In such setting thelongitudinal cutting edge I3 of said turning tool progressively seversthe lateral surfaces of the helical spring I1 from the end of bar Illa,While the downwardly and outwardly inclined cutting edge I3asimultaneously progressively forms said bar Ib and the opening 20, Fig.2, of spring I1, by progressively cutting the inner edge of springhelices I1 from the bar Illa, at the same time forming the turned barI0b at the end of bar Illa, and which bar Ib also supports the severedportion of the helical spring I1 from being Whipped about by the rapidrotation of bar Ia during the cutting of such spring, 'and therebyprecludes the breakage of the severed portion of the spring, as Well asinjury to persons and property therefrom. n

As shown in Figs. 9 and 10, the tool of Fig. 11 may be provided with aportion of a nick 2Ia, similar to one of the nicks 2I, in the point ofthe cutting edge I3 and a portion of a groove 22a, which, if complete,would be substantially like one of the grooves 22, extending along theouter end of the surface I6 of portion I4, with the bottom of saidgroove portion 22a. comprising the cutting edge I3. This produces at themargin of the central opening 20 through spring I1 a portion 23a. of acorrugation, which, if complete, may be substantially like thecorrugation 23. We have found that such corrugation 23a affordsadditional benefit and advantage to the spring I1 in increased strength,efficiency and freedom from breakage, as well as in finish or appearanceby additionally cold working the inner edge of the spring helicessimultaneously with its severance from the bar.

It will be understood that the spring I1 may be employed as acompression or an extension spring with equal advantage, in either ofwhich employments the aforesaid surfaces of the spring in helicalalignment with the force exerted upon such spring will be differentlycold worked, as heretofore described. It is also apparent that saidspring may also be advantageously employed as a torsional spring.

It will furthermore be understood by those skilled in the art that withno more skill, time or expense, but with little more power than requiredfo-r making a Waste shaving of substantially the same cross-sectionalarea, our invention produces very rapidly and cheaply a most efficientspring, having wide utility, great durability and economy.

The cutting edge I3, with or without the one or more nicks 2l thereinand associated grooves 22, in the cutting of metal exerts` considerablecompression stress upon the metal of the bar immediate-ly in advance ofthe actual progressive severance of the helical spring from the endthereof. This compression is localized progressively in the relativelysmall region in the end of the bar I0 or Iila, immediately in advanceand upon opposite sides of the cutting edge I3 of portion I4 of theturning tool shank I2. We have found in the turning of helical springsthat such compression is produced or substantially contributed to by thewide angle of the beveled or side rake surface I6 extending from suchcutting edge I3. Such compression, we have found, increases the densityof metal comprising the severed portion of the helical spring, as Wellas in the metal comprising the surface of the bar from which the severedportion of the spring was severed. We have also found that the one ormore nicks 2|v andi associated grooves 2v2l in and associated With thecutting edge ZInsubstantially increases saidcompressi'on; andresultingdensity in, the regiDn ofthe line of cleavage of metal being cut to formthe spring. These are substan.

tiar steps` in cold Working which we have found so beneficial andadvantageous in the production of springs. Immediately progressivelyfollowing saidcompression working of themetal occurs the beforementionedfurther cold Working of the metah` comprising the stretching and theburnishing: ofjthe metal of the surface of the spring as it is` sharplydeflected from the bar by sliding over the surface I6 of portion I4 ofthe shank I2 of the turningior cutting tool; while at the same time themetal of the opposite surface of spring I'I as it is cut from the end ofthe bar is compressed, increased in density and transformed from abright to a frosted appearance. 'I'he metal adjacent 'the surface of thegrooves or valleys 25, one or more of which may be in the spring I1, iscold Worked to a greater degree in and incident to the action thereon`of the nick or nicks 2| and accompanying groove or grooves 22 associatedwith said cutting edge I3, and said metal has a more pronounced frostedappearance. I'his additional cold Working is due to the stress ofarching the metal into the groove. This stress is at right angles to thebefore-stated arching at point I9 of Fig. 14 of the metal of the surfaceof the spring II which is out of contact with side surface or rake I6 oftool i2. 'Ihe arching of the metal of the severed spring at said pointI9 as Well as to form the groove 25 in spring I'E each cold works themetal of the spring I'I. The surface of severed spring Il, whichcontacts with the side rake or surface It of tool I2, by its arching ordeflection from bar I il or Illa, is further cold worked by beingslightly stretched as Well as burnished and rendered bright by itsforceful contact with and slidin over said surface I6. Y

The cutting or turning of the spring occurs at atmospheric temperaturewith no more heat than is generated by the cutting or turning operation.While the cutting or turning tool shown has afforded excellent resultsin the making of the sp-ring from copper, it Will be appreciated thatsimilar results may be obtained with other metals and alloys bysubstantially the same tool With,

such changes therein` as long practice has taught those skilled in theart to make in such tools when employed to cut different metals andalloys.

We have further found that the cold working of the metal to' an extentabove the elastic limit of such metal, and Which results in a permanenttransformation of its characteristics, is the kind of cold Working whichaffords the improved advantages and benefits of the metal which We havefound advantageous for spring purposes, although the same may becontributed to in some degree by Working or cold Working the metal belowsuch limit as may be incident to the beforestated working of the metalsimultaneously with its cutting.

It may be understood from the foregoing, by those skilled in the art,that the above described cold Working of the metal simultaneouslywithand by the manner of its cutting or turning produces a temporarystressing of the metal beyond its elastic limit and not beyond its pointof fracture, which substantially increases the strength and toughness ofthe metal at and adjacent the line of its cleavage. `Before ourinvention it Was, known that` solely by cutting or turning a unadaptedfor satisfactory or 4 useful spring service.` In our solution of saidproblem We employ such unadaptedand cheaper formof metal, and simply.expeditiously and inexpensively transform such metal of the constructedspring into those characteristics which We have found useful andadvantageous for spring purposes. As a part of such solution, We havebeen rst to make springs by a process of cutting or turning the springfrom a larger piece of metal. VIn such cutting or turning, We transformthev metal of the spring by stressing the metal beyond its elastic limitand below its fracture point. Under such stress a owage of the metaloccurs although the metal may be under atmospheric temperature exceptfor such stress. Such iiovvage cold works the metal of the spring andtransforms the same into characteristics which We have found veryeconomical and advantageous for spring purposes. Specifically, wesubject the metal to such stress as a part of our process of making thespring. Such process is by abnormally cutting or turning the spring froma larger piece of metal. The abnormalcy in such cutting or turningappears to reside in the fact that heretofore springs have not been somade, and further, that greater reluctance is designedly occasioned tothe passage of the cut or turned metal over and past the cutting orturning tool, and consequently the metal cut or turned is subjected togreater than normal stress at and adjacent the line of cleavage of themetal. Such greater reluctance and stress occasions the before-statedowage and cold Working of the metal at and adjacent the line of cleavageof the metal of the spring from a larger or thicker piece of metal. Wewere first to so cold Work the metal by and simultaneously with thecutting or turning of the same, by our process and tool, from a largerpiece of metal whose normal characteristics are unadapted for springpurposes, but which our said cold Working transforms intocharacteristics which we have found useful and advantageous for springsrequired in normal, as well as for some springs in severe serviceconditions. Such transformation by cold working the metal occurs in theshaving or portion cut or turned by our process and tool from the parentmetal, as Well as in the surface of the parent metal from which theshaving or portion was cut-or turned.

We are aware of a practice, termed Auto Frettage, of cold Working metalby directly applied hydraulic liquid pressure, which stresses the metalmanufactured into ordnance bores beyond its elastic limit and below itsfracture point, to increase its strength, but our invention'isradically/,different therefrom and a substantial improvement thereon. j

'I'his is a divisional application of our copending application SerialNo. 173,698 filed December 8, 1937.

The invention herein described may be manufactured and/or used by or forthe Government of the United VStates of America for governmentalpurposes Without the payment of any royalties thereon or therefor'. Y

We claim:

1. `A cut spring comprising an integral metallic member, the entirelateral surfaces of said member being formed by a cutting operation andcold Worked by the cutting.

2. A cut spring comprising an integral metallic member having at leastone corrugation extending longitudinally'thereof, the entire lateralsurfaces of said member being formed by a cutting operation and coldWorked by the cutting.

3. A cut spring comprising an integral metallic helical member, theentire lateral surfaces of said member being formed by a cuttingoperation and c old Worked by the cutting.

4. A cut spring comprising an integral metallic helical member having atleast. one corrugation extending longitudinally thereof, the entirelateral surfaces of said member being formed by a cutting operation andcold Worked by the cutting.

5. A out spring comprising an integral metallic member having at leastone registering projection and depression extending longitudinally alongopposite surfaces thereof, the entire lateral surfaces of said memberbeing formed by a cutting operation and cold worked by the cutting.

ALFRED J. BERG. JOI-1N O. HUSE.

